Click links below for a few prior NE threads that apply.
Read through for responses with reloading advice for the 9.5X57 / .375 Nitro Express Rimless and pay particular attention to those from Kuduae:

Kuduae Overkill

Loads

M1910 TD

Crackers

Newbie

Lead Loads

Reloading

9.5X57 Questions

9.5 X 57

Strippers

Unleaded

Deleted

And for general interest, specifications, ballistics, here are Mannlicher Schoenauer relevant images from the 1939 Stoeger catalog: MS 1939 Stoeger